1. Field of the Invention
The present invention relates to stabilizer compositions for halogen containing polymers, particularly polymers of vinyl chloride, and to polymeric formulations containing such compositions.
2. Background of the Invention
Halogen-containing polymers, more general by vinyl chloride polymers (PVC), are commonly used for wire insulation and cable jacketing purposes, particularly for use in office buildings and the like. In order to impart thermal stability to PVC insulation and/or cable jacketing, various thermal stabilizers are incorporated. In particular, lead salts have been used as thermal stabilizers in such PVC formulations. Along with providing heat stability, lead based stabilizers generally impart good electrical insulating properties to the polymeric formulation.
Because of increasing health and environmental concerns, attempts have been made to replace the lead based thermal stabilizers in PVC and other halogen-containing polymeric compositions. For example, a common PVC heat stabilizer comprises a mixture of antimony and tin salts. While these stabilizers are preferable to lead based stabilizers from a health and environmental viewpoint, they generally do not provide the electrical insulating properties which can be achieved using lead based thermal stabilizers.
Ideally, a thermal stabilizer for halogen-containing polymeric composition would contain no heavy metal salts, e.g. lead salts, but would impart thermal stability and electrical insulating properties equivalent or superior to those achieved with lead salts.